To increase the production, many factories have some new techniques.
| A．brought out | B．brought in | C．brought back | D．brought about |
_
_____ when to leave, I could only stay at home, _____ nothing.
| A．Knowing not; done | B．Not having known; doing |
| C．Having not known; done | D．Not knowing; doing |
While building a tunnel through the mountain, _____.
| A．an underground lake was discovered | B．workers discovered an underground lake |
| C．there was an underground lake discovered | D．a lake was discovered underground |
— I wonder if I could use your phone for a while?
— _____.
| A．It’s a good idea | B．Why not? Do it for yourself |
| C．Of course. Go ahead | D．It’s my pleasure |
Only when the war was over_______ to his hometown.
A. did the young soldier return B the young soldier returned
C. returned the young soldier D the young soldier returned
He is an hour late by now．He last night．
| A．must stay up | B．should stay up |
| C．should have stayed up | D．must have stayed up |